Disk drive device with versatile shaped core for rotating a disk

A disk drive device comprises a hub on which a magnetic recording disk is to be mounted; a base rotatably supporting the hub through a bearing unit; a sintered core fixed to the base, the sintered core having a ring portion and nine teeth that extend radially from the ring portion; coils wound around nine teeth; and a cylindrical magnet fixed to the hub. The sintered core is formed by heat-treating an iron powder. At least one of (a) the surfaces of particles of the iron powder and (b) the surfaces of the sintered core is insulated.